1. Field of Endeavor
The present invention refers to the field of turbomachines.
2. Brief Description of the Related Art
In turbines, especially steam turbines, a major problem is associated with the use of a split inner casing which is connectable by means of flanges, which problem is created as a result of the non-symmetrical casing geometry on account of the flanges. During the transition phases, and also in normal operation, unequal deformations of the inner casing occur as a result of the non-symmetrical geometry. The consequentially resulting gap between the stationary blade components, which are directly attached to the casing, and the rotating components, which are mounted on the rotor, is variable as a result. In order to prevent rubbing of the components, a minimum dimension for the gap, which occurs at the outset during assembly, has to be observed, which, during operation, leads to large regions with a greatly widened gap width on the casing circumference. The consequence of this is an increased steam leakage and an impaired blade action which is associated with it.
It has already been proposed in EP-A1-1 022 439 to homogenize the deformations of the casing which occur, by means of a variable thickness of the inner casing, in order to achieve a lessening of the gap problems. The outer casing, which concentrically encompasses the inner casing, remains unchanged in the case of this solution, which leads to unwanted changes in the interspace between the two casings.